Screen sharing between computing devices over a network has a myriad of practical applications. One practical application is collaboration between a host and a viewer. A host can give a presentation to one or more remote viewers, perform demonstrations, review documents, and share images. As an example of another practical use, screen sharing enables remote technical support. For example, by watching the keystrokes entered by a host, remote technical support staff can diagnose problems as though the present on site.
Often, during a screen-sharing session, the host can have several items visible on the desktop of the computer screen, which the hosts would prefer not to share, such items as icons, open applications, or browser windows. Before starting the screen-sharing session, the host would then need to remove or close such items. This is usually inconvenient and sometimes impractical. During other types of screen-sharing occasions, hosts may need to enter confidential information, such as a credit card numbers or personal identification numbers, which should not be shared.